The present invention relates to a magneto-resistance effect type magnetic head.
Today, more and more magneto-resistance effect type magnetic heads (called MR heads hereinafter) that excel in short wavelength sensitivity are being used illustratively as a reproducing magnetic head of the hard disc drive.
Where the magnetic head is a floating type, as shown in FIG. 6, there is provided a slider 52 that floats over a magnetic recording medium 51 (e.g., hard disc) thanks to the air flow created by relative motion of the medium 51 as it rotates. The slider 52 contains a conventional composite magnetic head 53 illustratively comprising an inductive type magnetic head for recording and an MR magnetic head for reproduction in an integral manner. The slider 52 also has a gimbal 53 composed of an elastic member for supporting the slider 52.
FIG. 7 is an enlarged partial cutaway perspective view of the composite thin film magnetic head 53. This magnetic head 53 is mounted on the above-described slider 52 or on a base 55 such as a substrate attached to the slider. The slider 52 or the base 55 comprises a first and a second thin film magnetic core 57 and 58 deposited one upon the other, the cores forming a magnetic gap (g) therebetween at the front ends thereof, the front ends facing the surface opposite to the magnetic recording medium 51, i.e., the air bearing surface (ABS) 56. Within the magnetic gap (g) is one end or one electrode 60a of a magneto-resistance effect sensing part 59 (called the MR sensing part) comprising at least a magneto-resistance effect thin film (called the MR thin film), the one end or electrode 60a facing the ABS 56.
Opposite to the ABS 56 is the other electrode 60b of the MR sensing part 59 substantially in parallel with the electrode 60a. Both electrodes 60a and 60b are made of conductive thin films. Across the approximate center of the MR sensing part 59 is a bias conductor 61 that energizes through an insulation layer 62 the MR sensing part 59 so that the latter is magnetized in a predetermined direction. The energizing is performed so that the MR sensing part 59 operates in a characteristic region representing high sensitivity and the linearity of excellent magneto-resistance effect. A head coil 63 surrounds a magnetic connection that serves as the contact between the thin film magnetic cores 57 and 58. The bias conductor 61 and the head coil 63 are both made of conductive thin films.
The thin film magnetic head 53 of the above-described construction is called the "composite" head because it comprises a shield type MR magnetic head and an inductive type magnetic head; the shield type MR magnetic head has the MR sensing part 59 between the first and second thin film magnetic cores 57 and 58; and the inductive type magnetic head contains the head coil 63 on the magnetic path formed by the first and second thin film magnetic cores 57 and 58.
As depicted in a schematic circuit diagram of FIG. 8, the MR magnetic head has one end of its MR sensing part 59 connected to ground potential Vss. A constant current source 64 supplies a sense current (is) across the electrodes 60a and 60b. In this setup, recordings on the magnetic recording medium 51 cause changes in resistance, the changes being detected as voltage changes.
The surface of the magnetic recording medium 51 develops and accumulates static electricity (i.e., electric charges) due to the air flow mentioned above. If the magnetic head 53 upon starting or stopping, comes sufficiently close to or contacts the surface of the magnetic recording medium 51, a discharge occurs between the ABS 56 of the grounded MR sensing part 59 and the end or the electrode 60a of the MR thin film opposite thereto. A large current triggered by the discharge flows into the MR thin film. That is, the electric charges accumulated on the magnetic recording medium 51 rush into the magnetic head and on to the MR thin film.
The MR thin film is a metal film as small as hundreds of angstroms in thickness to ensure its high sensitivity. The discharge current, if it flows in, destroys the MR thin film (called static electricity destruction).
It is therefore an object of the present invention to provide a magneto-resistance effect type magnetic head sufficiently reliable to avoid static electricity destruction due to the onrush of electric charges from the magnetic recording medium.